等温淬火对H13钢组织、硬度和拉伸性能的影响

Effect of isothermal quenching on microstructure,hardness and tensile properties of H13 steel

对H13钢进行不同工艺的等温淬火和回火处理,探讨了等温淬火工艺对H13钢组织、硬度和拉伸性能的影响。结果表明,随着等温温度的降低,显微组织中马氏体板条被逐渐增多的下贝氏体分割、细化;试样的硬度随着下贝氏体的增多而降低;抗拉强度与伸长率具有相同的变化趋势,即随下贝氏体的增加先提高后降低,在340℃等温75 min再进行560℃×2 h和540℃×2 h两次回火后均达到最大值,并相对于普通淬火分别提高了23.5%和36.2%,说明马氏体/下贝氏体(M/BL)复相组织中下贝氏体对H13钢拉伸性能的影响存在一个临界体积分数值。

Effects of isothermal quenching and tempering on microstructure,hardness and tensile properties of H13 steel were studied.The results show that with the decrease of isothermal temperature,the martensitic lath in microstructure of the H13 steel is segmented and refined by the increasing of the lower bainite.The hardness of the steel decreases with the increase of lower bainite.The tensile strength and elongation have the same variation trend,that is,with the increase of lower bainite,the tensile strength and elongation increase first and then decrease,and both reach the maximum value after isothermal holding at 340℃ for 75 min and then tempering at 560℃ for 2 h and at 540℃ for 2 h,which are increased by 23.5% and 36.2%,respectively,compared with that of the ordinary quenching.This indicates that there is a critical lower bainite volume fraction value for the effect of lower bainite in mixed microstructure of martensite and lower bainite(M/B_(L))on the tensile properties of the H13 steel.